lab 7

Lab 7: Conservation of Momentum and Energy Clayton mccall October 20 th 2023 Page 1 of 7

Objective: Create an experiment with two balls and a measuring tape to learn how to find impact velocity, coefficient of restitution, and rebound velocity with the data you get from dropping the balls separately and together one on top of the other. Data Section Data Table 1 Mass of Sports Balls Type of Sports Ball Mass [kg] Tennis Ball .0564 Ping Pong Ball .0028 Part 1: in part one I had the tennis ball and dropped it at a certain height 48in(1.2192m) and used data collected to find impact velocity, coefficient of restitution, and rebound velocity. To find the impact velocity I used the formula √(2*g*height of drop). When plugged in you get √(2*9.8*1.2192)=4.888. and since I used the same height on all of the trials the impact velocity stays the same Data Table 2 Part I Single Ball Drop – Tennis Ball Type of Sports Ball: Initial Height [m] Impact Velocity [m/s] Rebound Height [m] Coefficient of restitution (COR) = √ Rebround Heei Initial Drop Hei Rebound Velocity = Impact Velocity x COR [m/s] height h 1 1.2192 4.888 .6604 .7360 3.5976 height h 2 1.2192 4.888 .6858 .75 .3.666 height h 3 1.2192 4.888 .7366 .7773 3.7994 Part 2: Page 2 of 7

Data Table 4 Part II Stacked Ball Drop Initial Height both balls [m] Impact Velocit y of Ping Pong Ball v i [m/s] Impact Velocity of Tennis Ball V i [m/s] Rebound Height Ping Pong Ball [m] Rebound Velocity of Ping Pong Ball v f [m/s] Rebound Height Tennis Ball [m] Rebound Velocity of Tennis Ball V f [m/s] height h 1 1.2192 4.888 4.888 2.032 6.3104 .5334 3.2331 height h 2 1.2192 4.888 4.888 1.9812 6.231 .635 3.5276 height h 3 1.2192 4.888 4.888 2.0828 6.3888 .4826 3.0753 Stacked Ball Drop Questions 1. Describe how the momentum of a single ball changes as it free falls from a height of approximately 1 m, collides with a hard floor, and rebounds. When the ball hits the floor a lot of the energy that comes from the ball being dropped at 1m goes into the floor and is lost which means (depending on the Page 4 of 7

consistency of the ball and the floor) the ball should bounce to a lower height than it was dropped from. 2. When the single ball (wither the tennis ball or the ping pong ball) hits the floor, a collision occurs between the ball and the floor. Is the collision elastic or inelastic? Describe how you determine whether a collision is elastic or inelastic. In the case of the ping pong ball hitting a hard floor the collision would be elastic the reason why this would be elastic is because of the consistency of the floor and the ping pong ball. Because the constancies make an energy conversion where the two bounce of of each other momentum and kinetic energy are both conserved and the ball bounces of the floor. 3. In a closed system the total momentum before a collision is equal to the total momentum after the collision. Does your data from Part I Single Ball Drop support this statement? If not, explain why. No this is not true of my ball drop. The reason why is because when the ball hits the ground some of its energy gets absorbed by the floor and the momentum is slowed down while in a closed system energy would not be absorbed and would stay the same. 4. A ping pong ball and a tennis ball are dropped and there is a very small gap between them when the tennis ball hits the floor. Indicate the directions of the momentums of the ping pong ball and the tennis ball after the tennis ball collides with the floor, but before the balls collide with each other. (Drawing a diagram may be helpful.) Just after the tennis ball collides with the floor the tennis ball starts to move up in momentum. The ping pong ball is still falling and has a downward momentum. The two balls momentum is opposite up until the ping pong ball collides with the tennis ball . 5. Explain why the rebound heights of the ping pong ball in Part II Stacked Ball Drop are greater than the rebound heights of the ping pong balls from Part I Single Ball Drop. The rebound heights in the stacked ball experiment are higher than the rebound heights in the first parts because the object the ping pong ball collides into has momentum going up which makes the ping pong ball move faster and higher than it would if it was colliding with the floor. Page 5 of 7

In this lab I feel that even though I did not do any calculations to calculate my accuracy my values were fairly accurate. The one place where I do not feel so confident is my values on the stacked ball experiment. I feel that in the stacked ball experiment the values I found were difficult to find because I had to calculate more and it was more difficult to read my video for the stacked ball experiment. Results and interpretation: In this lab I was supposed to learn how to find impact velocity, rebound velocity and coefficient of restitution. I feel like I learned what I sought out to learn in this lab and I feel like I did the lab how I was supposed to. I feel like my results came out with a good accuracy and where very simple to calculate correctly. Conclusion: This lab was very fun to go through and was very interesting. I've always loved playing wall ball when I was little at school and now it feels good to know that I would be able to calculate the rebound velocity and impact velocity of the wall ball. I feel like I learned a lot going through this lab and what I wanted to do was achieved. Although I did like this lab there were labs that were diferent from this one that I liked more. Overall I enjoyed this lab and I am looking forward to learning more in the future in labs like this one. References: Walker, J., Resnick, R., & Halliday, D. (2014). Fundamentals of physics . John Wiley & Sons, Inc. Page 7 of 7